Blackmailing my Big Step-Sister Into Fucking Me in the Back Yard

I heard some noise outside the house, when I went in the back yard I find my big step-sister Kat struggling to get out her window. Kat has been grounded for a while and is not supposed to be going out, I tell Kat if she wants me to keep my mouth shut she is gonna have to do something for me. Their is only one thing on my mind, Kat's tight pussy. I tell her for me to keep my mouth shut she is gonna have to fuck me right there in our back yard. My step-sister is such a slut she does everything I want and more, I even fill up her tight pussy with a nice big load.